Modulating compression release for an engine

ABSTRACT

A device and method of controlling the release of pressure from an engine combustion chamber. The compression release device has a hand controlled valve at the entrance to a passage through the device to an opening to atmosphere. A projection from the valve restricts flow through the passage during part of the travel by the valve stem, and a reed valve covers the opening to atmosphere to act as a check valve. Also disclosed is a second valve rigidly mounted to the valve stem which closes when the first valve is opened and the valve stem is at its end of travel.

1 1 Dec. 30, 1975 United States Patent 11 1 Peterson l l MODULA'I'ING COMPRESSION RELEASE FOR AN ENGINE |76| Inventor: Brent 1,. Peterson, 2916 River Road, Primary Examiner-Wendell Bums Tacoma, Wash.

Nov. 5, 1973 Assistant l-.'xamint-r1)avid D. Reynolds Attorney, Agent, or I"irmMorris A. Case [22] Filed:

ABSTRACT I21] Appl. No.: 412,800

123/182 A device and method of controlling the release of pressure from an engine combustion chamber. The compression release device has a hand controlled valve at the entrance to a passage through the device |5o| References Cit d to an opening to atmosphere. A projection from the f5 o wmm t l n )fl0fl wa m k m v cmum n. a..mwe a a w mv SVJ SI 0 Si m r 3 cl p mar m 630 Hn ae hmmvh m u ne. oe VSCS h m wm Vm mC 0 e a i mo ul m w .mb 1.ml m menc www q 2 eU e v..uv MMM M vIlAv 2 XV X 53I2 O X R32 2 3 5 .2 2. .l

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and the valve stem is at its end of travel.

5/1964 United Kingdom................. 251/122 24 Claims, 13 Drawing Figures U.S. Patent Dec. 30, 1975 Sheet 1 of 3 3,929,116

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KWWVL US. Patent Dec. 30, 1975 Sheet 2 of 3 3,929,116

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MODULATING COMPRESSION RELEASE FOR AN ENGINE BACKGROUND OF THE INVENTION.

It is known to mount a compression release device to an engine head of a vehicle such as a motorcycle. The device has an interior opening communicating from the compression chamber to atmosphere. In its simplest form the device has a valve located at the entrance to the opening and has a valve stem extending from the entrance up through a housing where the end of the valve stem is controlled with a spring holding the valve closed and a hand operated cable working against the spring to open the valve. When the vehicle is in operation the valve is closed, and when one wishes to brake the vehicle the valve is opened for compression release to give a very effective braking action. Difficulties were experienced with these devices due to foreign matter being ingested into the engine during the intake or suction travel of the engine piston. It is known to use filters on the outlet to atmosphere to try to prevent ingestion, but this has been only partially successful. In US. Pat. No. 3,638,632 a second valve was slideably mounted to the valve stem and was backed with a spring to act as a check valve and prevent entry of foreign material. In U.S. Pat. No. 3,707,952 the outlet was biased upwardly through a plurality of openings each of which held a captive ball which acted as a check valve. In the instant invention a reed has been placed over the opening to the atmosphere to give a simpler more trouble free check valve. These compression release units provide effective braking which in combination with the brakes actuated by the foot pedals provide very good braking even in an emergency. Motorcycles are often used in cross country operation. In such use and when going down hill the compression release is too effective, and in order to properly descend the release must be opened and closed as one descends. It was discovered a controlled braking could be obtained by placing a restriction in the opening through'which the gases pass to give modulated control of the flow by a setting of the valve to give the desired amount of braking.

SUMMARY OF THE INVENTION An interior passage extends longitudinally part way through the compression release device and communicates with a lateral channel which opens to the atmosphere. A valve seat is located at, the entrance to the passage, a valve plug mates with the seat and has a valve stem which extends longitudinallythrough and is centered in the passage. The valve stem has an enlarged section adjacent the plug which extends part way into the passage. When the valve is opened slightly the enlarged section restricts flow in the passage. When the valve is opened more the enlarged section still restricts, but allows a greater rate of flow of the gases. When opened further the enlarged section is moved out of the passage to give unrestricted flow. A reed is placed over the opening to atmosphere, and a cover is placed over the reed to limit its outward travel.

An object of this invention is to provide a compression release valve having a reed covering its opening to atmosphere to prevent ingestion of foreign material.

Another object is to provide a compression release valve which may be modulated to control the rate of flow of gases therethrough.

Another object of this invention is to provide a method to control the rate of flow of gases and to prevent the ingestion of foreign material when using compression release to control braking of a vehicle.

Yet another object of this invention is to provide a compression release valve that may be modulated to control the rate of flow of gases therethrough to assist in starting an engine.

Other objects and various advantages will be apparent from the following description and drawing which are submitted for purposes of illustration only and are not intended to be limiting.

DESCRIPTION OF THE DRAWINGS FIG. 1 shows a schematic perspective view of the compression release device mounted on a motorcycle.

FIG. 2 shows a perspective view of the device mounted to an engine head.

FIG. 3 shows a vertical cross-sectional view of the device of FIG. 2.

FIG. 4 is an exploded perspective view of the device of FIG. 2.

FIG. 5 shows a side elevational view in section of an alternate embodiment of the compression release device.

FIG. 6 shows a sideelevational view partially in section of yet another embodiment.

FIG. 7 shows a fragmented side elevational sectional view of an alternate embodiment of the valve partof FIG. 3. 7

FIG. 8 shows a fragmented side elevational sectional view of yet another embodiment of the valve part of FIG. 3.

FIG. 9 shows a fragmented side elevational sectional view of an alternate embodiment of the modulating valve part of FIG. 5.

FIG. 10 shows a fragmented side elevational sectional view of yet another embodiment of the modulating valve part of FIG. 5.

FIG. 11 shows a perspective view of a U-shaped cover section for a compression release device.

FIG. 12 shows an exploded perspective view of part of a compression release device using the U-shaped cover of FIG. 11.

FIG. 13 shows a fragmented vertical cross-sectional view of the compression release device of FIG. 12.

DETAILED DESCRIPTION In FIG. 2 compression release device 10, is mounted to engine head 12. The casing 'on housing 14, is threaded 16 at one end to permit mounting into the engine head. The housing has a centrally located passage 18 that extends longitudinally part way into the housing where it joins laterally extending channels or openings 20a and 20b which open to the atmosphere at 22a and 22b respectively. These openings are covered with reeds 24a and 24b which are shaped to match the contour of the outside of the casing at the opening. These reeds are made from a material that will flex to move out against a cover 26a and 26b in response to the pressure of gases moving outward through the opening, and will return to position to seal the openings when the piston in the engine moves inward to create a suction into the engine. Thus, the reeds prevent foreign matter from being ingestedinto the engine. The reed and the cover plate are fastened to the housing at 28a and 28b which is threaded to accept screws 30a and 30b which fastens through lock washers 32a hole 34a in 3 the cover and hole 36a of the reed, and lock washer 32b, hole 34b and hole 36b respectively. Valve seat 38 is located at the entrance to the passage and mates with tapered surface 40 of plug 42. This plug is connected to valve stem 44 which is centered in passage 18 extends up through hole 46 in the housing and is threaded at 48 for screwing into retainer cap 50. Spring 52 seats in recess 54 of housing 14 and extends to the projection 56 on the retainer cap. A covering for flexible cable 60 bottoms out in recess 62 of the cap and the cable extends on down into recess 64 of the housing where screw 66 holds it in place. In this embodiment the valve stem has a raised section 68 adjacent the tapered surface 40 and a smaller raised section 70 adjacent the first raised section both of which extend into the passage when the valve is closed or partially opened. Passage 18 has an enlarged diameter 72 for a distance in from the end to accommodate the first raised section.

In operation the compression release device is mounted to the engine head 12 of a vehicle 73 such as a motorcycle. Flexible cable 60 with cover 58 extends up to and is joined to the handle bar 74 where lever 76 is used to move the cable and operate the valve. When the lever is released the spring 52 keeps the tapered surface 40 of the plug against the valve seat 38 and the valve is closed. To decelerate the moving vehicle the lever is actuated to move the valve plug off the valve seat. When the valve is moved to the wide open position gases are dumped to atmosphere through the passage when the engine piston is moving outward and is prevented from entering by the reed valve 24 when the piston moves inward. When the plug contact surface moves off the valve seat a short distance the stem raised section 68 restricts flow through the passage and the vehicle is braked by the flow of gases, but at a reduced rate. As the valve is opened more the rate of flow of gases is increased and the rate of braking is also increased. When the valve is moved to clear the raised section from the passage maximum flow and maximum braking is obtained.

In another embodiment as shown in FIG. 5, compression release unit 78 has sleeve 80 which has interior passage 82, with valve seat 84 at one end and valve seat 86 at the other end of the passage. Thus, two alternatively acting valves are operated off one valve stem 88 with valve plug 90 for closing off one end of the passage and valve plug 92 for closing off the other end. Plug 92 is rigidly attached to the valve stem by set screw 94 which bottoms in indent 96 in the valve stem, and hole 98 extends through the plug to permit a controlled movement of gases therethrough when the plug is seated. This hole is used to modulate the flow of gases to control the stopping by engine compression, and may also be used to give a controlled pressure buildup when starting the engine to make it easier to start. The passage communicates with chamber 100 which is enlarged to permit movement of the plug, and thence communicates with lateral channels 102a and 10% which opens to the atmosphere. The openings 103a and l03b are covered with reeds 104 a and l04b respectively; which in turn have their outward travel limited by curved cover plates 106a and 106b. In this embodiment control cable 108 has ball 110 rigidly fastened thereto, and the cable is fastened to housing 112 with slot 114 which. is wide enough to permit the cable to pass through, but is too narrow to permit the ball to pass through.

In operation a lever 76 such as shown in FIG. 1 is positioned to act against spring 116 and move plug 92 against the valve seat 86. Hole 98 makes it easy to start the engine. Once started the lever moves to permit the spring to take over, and now valve plug is seated against valve seat 84 while the engine is in operation. When one wishes to effect maximum engine braking the valve stem is moved so that neither valve is seated, and when one wishes a reduced magnitude of braking plug 92 is seated. The reeds act as a check valve to prevent the ingestion of foreign matter.

In another embodiment as shown in FIG. 6 a modified and modulating plug 118 is rigidly attached to valve stem 88 with a set screw 120, the plug has three stepped cross-sectional areas with the largest being 122, next 124 and the third 126. The transition between 122 and 124 is an area 128 which mates with valve seat 130 of a modified sleeve 132. The sleeve modification has an enlarged opening 134 to passage 136. All other parts on this embodiment are identical to and are numbered the same as the parts shown in FIG. 5. In operation disc or plug 118 is moved a small distance off the valve seat 130. At this valve position area 124 all but fills volume 134, and it assists in starting the engine. Once the engine is started the valve stem is moved to bring plug 90 into contact with the seat 84. When one wishes to brake the vehicle with the engine lever 76 is moved to seat plug 118 then backed off to obtain the amount of braking desired. To obtain full braking the plugs are positioned to give free flow through the passage.

In FIGS. 7 through 10 are shown alternate embodiments of modulating valve arrangements for selectively controlling the flow of gases through the compression release device. FIGS. 7 and 8 are alternate embodiments of the valve part of FIG. 3. In FIG. 7, housing 14 has passage 18 with a uniform diameter throughout its length. Valve stem 44 has an enlarged section 138 which is contiguous to tapered surface 40. The enlarged section may be slightly tapered, but in this embodiment it has a uniform diameter which is preferably about 0.0005 to 0.0l0 inch less than the inside diameter of the passage. In FIG. 8 an enlarged section 140, of valve stem 44, is shaped as the frustum of a cone and tapers from the base of the tapered surface 40, to the constant diameter of the valve stem. FIGS. 9 and 10 are alternate embodiments of the valve part of FIG. 5. In both FIGS. 9 and 10 the valve plug 92 of FIG. 5 is modified by eliminating the hole 98 and by adding a projection which extends down into the passage 82 to restrict flow of gases through the passage. In FIG. 9 the projection 142 has essentially a constant diameter which preferably is about 0.0005 to 0.0l0 inch smaller than the inside diameter of the passage. The projection 144 of FIG. 10 is shaped like an inverted frustum of a cone.

FIGS. 11, 12 and I3 depict yet another embodiment of a modulating compression release device. Housing 146, has passage 148 extending upward from a modulating valve, not shown, which may be any of the variations previously covered. The passage communicates with oppositely located lateral extending channels 150a and 15% which open to atmosphere at openings 152a and 152b. The openings are covered with reeds 154a and 154b. A one piece U-shaped cover 156 is fastened to the housing with bolts 158a and l58b. The base 160, of the U has hole 162 for accepting valve stem 164, and the base extends over the end 166 of the housing, and

legs 168a and 1681; extend down the sides of the housing to cover and to limit the outward movement of the reeds. The legs are curved outward to impart smooth stoppage of the reeds. The U-shaped cover has slot 170 extending along the base and part way down leg 168b, and has enlarged area 172 at its lower end. Cable 174 has ball 176 rigidly fastened thereto. The ball will pass through enlarged area 172 but is too large to go through the rest of the slot. This permits rapid fastening of the cable to the cover. In this embodiment opening 178 in the housing permits entry of the ball. Space for the ball may be provided by raising the cover before fastening to yield room between the top of the housing and the base of the U-shaped cover. In operation a lever as shown at 76 in FIG. 1, moves the cable 174 to compress the spring 180, moves the valve stem and actuates the valve.

I claim:

1. A device for connection to a head of an engine for compression release from the top of an engine cylinder comprising:

a. a housing one end of which has means for fastening to an engine head and having a passage extending longitudinally from inside a compression chamber to communicate through at least one lateral opening to atmosphere,

b. a first valve at an entrance to the longitudinal passage having a valve stem centered in the longitudinal passage.

c. a reed fastened to the housing and located to cover the lateral opening,

d. means for acting on the valve stem to control the first valve.

e. means for restricting the clearance between the stem and the passage to control the flow of gases therethrough, wherein the means for restricting the clearance comprises:

f. an enlarged cross section in the longitudinal passage immediately adjacent the entrance therein,

g. a first enlarged section on the stem contiguous to the valve, and

h. a second smaller enlarged section on the stem contiguous to the first enlarged section.

2. A device for connection to a head of an engine for compression release from the top of an engine cylinder comprising:

a. a housing one end of which has means for fastening to an engine head and having a passage extending longitudinally from inside a compression chamber to communicate through at least one lateral opening to atmosphere,

b. a first valve at an entrance to the longitudinally extending passage having a valve stem centered in the longitudinal passage.

c. a reed fastened to the housing and located to cover the lateral opening,

d. means for acting on the valve stem to control the first valve and e. a second valve attached to the valve stem and located at an outlet to the longitudinal passage.

3. A device as in claim 2, wherein the second valve comprises:

a. a valve seat at the outlet end of the longitudinal passage, and

b. a plug rigidly fastened to the valve stem for mating with the valve seat having a hole for communicating therethrough to allow a controlled flow of gases through the seated plug.

4. A device as in claim 2, whereinthe passage is enlarged near its outlet and the second valve comprises a valve seat at the end of the passage and a valve plug rigidly fastened to the valve stem, said plug having three stepped cross-sectional areas with the transition area between the largest and second largest areas mating with the valve seat, and the periphery of the second largest area extending into and being slightly less than the periphery of the enlarged part of the passage.

5. A device for attachment to an engine head to modulate compression release from the top of an engine cylinder comprising: a housing one end of which has means for fastening to an engine head and having a uniform diameter interior passage extending part way in from the fastened end thence communicating with at least one lateral channel opening to atmosphere; a valve seat located at an entrance to the passage; a valve plug to mate with the valve seat having a valve stem centered in the passage; an enlarged section on the valve stem immediately adjacent the valve plug to restrict the flow of gases through said passage, said enlarged section having a diameter less than the diameter of the interior passage, means for controlling the valve and valve stem throuh all phases from closed, open and enlarged section restricting varying amounts depending on its position and open with enlarged section clear of the passage to permit unrestricted flow; and a reed located to cover the opening to atmosphere to act as a check valve allowing gases to flow outward and closing on each intake cycle of an engine piston to prevent foreign matter being sucked into the engine.

6. A device as in claim 5, further comprising a cover over the reed to limit its outward travel.

7. A device for attachment to an engine head to modulate compression release from the top of an engine cylinder comprising: a housing one end of which has means for fastening to an engine head and having an interior passage extending part way in from the fastened end thence communicating with at least one lateral channel opening to atmosphere; a valve seat located at an entrance to the passage; a valve plug to mate with the valve seat having a valve stem centered in the passage; an enlarged section on the valve stem immediately adjacent the valve plug to restrict the flow of gases through said passage; means for controlling the valve and valve stem through all phases from closed, open and enlarged section restricting varying amounts depending on its position and open with enlarged section clear of the passage to permitunrestricted flow; a reed located to cover the opening to atmosphere to act as a check valve allowing gases to flow outward and closing on each intake cycle of an engine piston to prevent foreign matter being sucked into the engine; and a second lateral channel opening on the opposite side of the housing from the first lateral opening, a second reed covering the second opening, a U-shaped section fastened to the housing with the base extending over an open end of the housing and the legs extending down the sides of the housing to limit the outward travel of the reeds.

8. A device as in claim 7 further comprising: means for utilizing the U-shaped section as part of the means for controlling the valve and valve stem.

9. A- deviceas in claim 7, wherein the enlarged section on the valve stem further comprises at least two stepped areas with the largest area adjacent the valve plug.

10. A device for attachment to an engine head to modulate compression release from the top of an engine cylinder comprising: a housing one end of which has means for fastening to an engine head for communication to a compression chamber at the top of the engine cylinder the housing having an internal longitudinal passage extending from the fastened end part way into the housing, thence communicating with an enlarged chamber, which in turn communicates with at least one lateral channel opening. to atmosphere; a first valve, normally closed when operating the engine, located at an entrance to the longitudinal passage having a valve stem extending through and centrally located in the passage; a second valve located at the outlet to the longitudinal passage comprising a valve plug rigidly fastened to the valve stem closes with the first valve open and the valve stem at its limit of travel; and a reed covering the opening to atmosphere acts as a check valve.

11. A device as in claim 10, further comprising means to allow a restricted flow of gases through the plug of the second valve when said valve is closed.

12. A device as in claim 10, wherein the second valve plug further comprises: a projection extending part way down into the passage to restrict flow therethrough when the plug on the second valve is moved a short distance off the valve seat, and will clear the passage upon further movement.

13. A device as in claim 12, wherein the projection is stepped to have at least two different cross-sectional areas.

14. A method of controlling compression release from an engine on a vehicle, the steps comprising:

a. connecting a compression release device onto a head of an engine to communicate with an engine compression chamber,

b. opening a valve in the release device to allow gases to pass from the compression chamber through a passage-inside the device and thence out to atmosphere to provide an engine braking effect as the gases are released.

c. utilizing a reed type valve at the opening to atmosphere to prevent backward flow of gases during the intake cycle of the piston and thereby prevent the ingestion of foreign matter,

d. placing a second valve in the passage for closing the passage when the first valve is open.

15. A method as in claim 14, with the additional step of utilizing an opening through the second valve to allow restricted flow through of gases when the second valve is closed.

16. A method as in claim 14, with the additional step of partially blocking the passage when the second valve is opened slightly to restrict and thereby control the flow of gases.

17. A device for attachment to an engine head for compression release from the top of an engine cylinder comprising: a housing one end of which has means for fastening to an engine head and having a passage extending longitudinally frominside a compression chamber to communicate with a pair of oppositely extending lateral openings to atmosphere, a reed located to cover each of the openings to atmosphere, a U-shaped section fastened to the housing with base extending over an end of the housing and legs extending down sides of the housing to limit outward travel of the reeds, a valve at an entrance to the longitudinal passage having a valve stem centered in the passage, and means for acting on the valve stem to control the valve.

18. A device as in claim 17 further comprising: an enlarged section on the stem contiguous to the valve.

19. A device as in claim 18 wherein the enlarged section has a diameter about 0.005 to 0.010 inch smaller than the inside diameter of the passage.

20. A device as in claim 18 wherein the enlarged section has a shape of an inverted frustum of a cone.

21. A device as in claim 18 further comprising means for utilizing the U-shaped section as part of the means for acting on the valve stem to control the valve.

22. A device for attachment to an engine head as in claim 5 wherein the diameter of the enlarged section on the valve stem is about 0.005 to 0.010 inch smaller than the inside diameter of the passage.

23. In an improvement of a device for attachment to a head of a two cycle engine with the device having a first valve and an opening to a passage for communication from a top of a cylinder in the two cycle engine to an opening to atmosphere, a hand operated attachment for controlling the valve and a second valve automatically responsive to close the opening to atmosphere during an intake cycle of a piston wherein the improvement comprises: a uniform diameter to the passage contiguous to the opening from the top of the cylinder, a stem connected to the first valve and centered in the uniform diameter passage, an enlarged section on the stem slightly tapered from a diameter contiguous to the first valve of about 0.005 to 0.0l0 inch less than the inside diameter of the passage to restrict and modulate flow of gases through the passage.

24 In an improvement of a device as in claim 23 wherein the automatically responsive second valve comprises and covering the opening to atmosphere. 

1. A device for connection to a head of an engine for compression release from the top of an engine cylinder comprising: a. a housing one end of which has means for fastening to an engine head and having a passage extending longitudinallY from inside a compression chamber to communicate through at least one lateral opening to atmosphere, b. a first valve at an entrance to the longitudinal passage having a valve stem centered in the longitudinal passage. c. a reed fastened to the housing and located to cover the lateral opening, d. means for acting on the valve stem to control the first valve. e. means for restricting the clearance between the stem and the passage to control the flow of gases therethrough, wherein the means for restricting the clearance comprises: f. an enlarged cross section in the longitudinal passage immediately adjacent the entrance therein, g. a first enlarged section on the stem contiguous to the valve, and h. a second smaller enlarged section on the stem contiguous to the first enlarged section.
 2. A device for connection to a head of an engine for compression release from the top of an engine cylinder comprising: a. a housing one end of which has means for fastening to an engine head and having a passage extending longitudinally from inside a compression chamber to communicate through at least one lateral opening to atmosphere, b. a first valve at an entrance to the longitudinally extending passage having a valve stem centered in the longitudinal passage. c. a reed fastened to the housing and located to cover the lateral opening, d. means for acting on the valve stem to control the first valve and e. a second valve attached to the valve stem and located at an outlet to the longitudinal passage.
 3. A device as in claim 2, wherein the second valve comprises: a. a valve seat at the outlet end of the longitudinal passage, and b. a plug rigidly fastened to the valve stem for mating with the valve seat having a hole for communicating therethrough to allow a controlled flow of gases through the seated plug.
 4. A device as in claim 2, wherein the passage is enlarged near its outlet and the second valve comprises a valve seat at the end of the passage and a valve plug rigidly fastened to the valve stem, said plug having three stepped cross-sectional areas with the transition area between the largest and second largest areas mating with the valve seat, and the periphery of the second largest area extending into and being slightly less than the periphery of the enlarged part of the passage.
 5. A device for attachment to an engine head to modulate compression release from the top of an engine cylinder comprising: a housing one end of which has means for fastening to an engine head and having a uniform diameter interior passage extending part way in from the fastened end thence communicating with at least one lateral channel opening to atmosphere; a valve seat located at an entrance to the passage; a valve plug to mate with the valve seat having a valve stem centered in the passage; an enlarged section on the valve stem immediately adjacent the valve plug to restrict the flow of gases through said passage, said enlarged section having a diameter less than the diameter of the interior passage, means for controlling the valve and valve stem throuh all phases from closed, open and enlarged section restricting varying amounts depending on its position and open with enlarged section clear of the passage to permit unrestricted flow; and a reed located to cover the opening to atmosphere to act as a check valve allowing gases to flow outward and closing on each intake cycle of an engine piston to prevent foreign matter being sucked into the engine.
 6. A device as in claim 5, further comprising a cover over the reed to limit its outward travel.
 7. A device for attachment to an engine head to modulate compression release from the top of an engine cylinder comprising: a housing one end of which has means for fastening to an engine head and having an interior passage extending part way in from the fastened end thence communicating with at least one lateral channel opening to atmosphere; a valve seat located at an eNtrance to the passage; a valve plug to mate with the valve seat having a valve stem centered in the passage; an enlarged section on the valve stem immediately adjacent the valve plug to restrict the flow of gases through said passage; means for controlling the valve and valve stem through all phases from closed, open and enlarged section restricting varying amounts depending on its position and open with enlarged section clear of the passage to permit unrestricted flow; a reed located to cover the opening to atmosphere to act as a check valve allowing gases to flow outward and closing on each intake cycle of an engine piston to prevent foreign matter being sucked into the engine; and a second lateral channel opening on the opposite side of the housing from the first lateral opening, a second reed covering the second opening, a U-shaped section fastened to the housing with the base extending over an open end of the housing and the legs extending down the sides of the housing to limit the outward travel of the reeds.
 8. A device as in claim 7 further comprising: means for utilizing the U-shaped section as part of the means for controlling the valve and valve stem.
 9. A device as in claim 7, wherein the enlarged section on the valve stem further comprises at least two stepped areas with the largest area adjacent the valve plug.
 10. A device for attachment to an engine head to modulate compression release from the top of an engine cylinder comprising: a housing one end of which has means for fastening to an engine head for communication to a compression chamber at the top of the engine cylinder the housing having an internal longitudinal passage extending from the fastened end part way into the housing, thence communicating with an enlarged chamber, which in turn communicates with at least one lateral channel opening to atmosphere; a first valve, normally closed when operating the engine, located at an entrance to the longitudinal passage having a valve stem extending through and centrally located in the passage; a second valve located at the outlet to the longitudinal passage comprising a valve plug rigidly fastened to the valve stem closes with the first valve open and the valve stem at its limit of travel; and a reed covering the opening to atmosphere acts as a check valve.
 11. A device as in claim 10, further comprising means to allow a restricted flow of gases through the plug of the second valve when said valve is closed.
 12. A device as in claim 10, wherein the second valve plug further comprises: a projection extending part way down into the passage to restrict flow therethrough when the plug on the second valve is moved a short distance off the valve seat, and will clear the passage upon further movement.
 13. A device as in claim 12, wherein the projection is stepped to have at least two different cross-sectional areas.
 14. A method of controlling compression release from an engine on a vehicle, the steps comprising: a. connecting a compression release device onto a head of an engine to communicate with an engine compression chamber, b. opening a valve in the release device to allow gases to pass from the compression chamber through a passage inside the device and thence out to atmosphere to provide an engine braking effect as the gases are released. c. utilizing a reed type valve at the opening to atmosphere to prevent backward flow of gases during the intake cycle of the piston and thereby prevent the ingestion of foreign matter, d. placing a second valve in the passage for closing the passage when the first valve is open.
 15. A method as in claim 14, with the additional step of utilizing an opening through the second valve to allow restricted flow through of gases when the second valve is closed.
 16. A method as in claim 14, with the additional step of partially blocking the passage when the second valve is opened slightly to restrict and thereby control the flow of gases.
 17. A device for attachment to an engine head for compression release from the top of an engine cylinder comprising: a housing one end of which has means for fastening to an engine head and having a passage extending longitudinally from inside a compression chamber to communicate with a pair of oppositely extending lateral openings to atmosphere, a reed located to cover each of the openings to atmosphere, a U-shaped section fastened to the housing with base extending over an end of the housing and legs extending down sides of the housing to limit outward travel of the reeds, a valve at an entrance to the longitudinal passage having a valve stem centered in the passage, and means for acting on the valve stem to control the valve.
 18. A device as in claim 17 further comprising: an enlarged section on the stem contiguous to the valve.
 19. A device as in claim 18 wherein the enlarged section has a diameter about 0.005 to 0.010 inch smaller than the inside diameter of the passage.
 20. A device as in claim 18 wherein the enlarged section has a shape of an inverted frustum of a cone.
 21. A device as in claim 18 further comprising means for utilizing the U-shaped section as part of the means for acting on the valve stem to control the valve.
 22. A device for attachment to an engine head as in claim 5 wherein the diameter of the enlarged section on the valve stem is about 0.005 to 0.010 inch smaller than the inside diameter of the passage.
 23. In an improvement of a device for attachment to a head of a two cycle engine with the device having a first valve and an opening to a passage for communication from a top of a cylinder in the two cycle engine to an opening to atmosphere, a hand operated attachment for controlling the valve and a second valve automatically responsive to close the opening to atmosphere during an intake cycle of a piston wherein the improvement comprises: a uniform diameter to the passage contiguous to the opening from the top of the cylinder, a stem connected to the first valve and centered in the uniform diameter passage, an enlarged section on the stem slightly tapered from a diameter contiguous to the first valve of about 0.005 to 0.010 inch less than the inside diameter of the passage to restrict and modulate flow of gases through the passage.
 24. In an improvement of a device as in claim 23 wherein the automatically responsive second valve comprises a reed covering the opening to atmosphere. 